Allow passing options hash to a custom validator.
Calling  will now return the current content-type.
Filled out some specs for #716.
Enable RSpec rerun with Guard.
Fixed documentation for redirect

Default in doc was true but in code it was false.
Errors can now be presented with a Grape::Entity class.
Merge pull request #724 from GvS666/master

Fixed documentation for redirect
added doc for how to use ActionDispatch::RemoteIp refs: #648